The human immune system, when appropriately stimulated, has the capacity to recognize and destroy cancer cells. While many pathways of tumor killing have been identified, the most potent is that mediated by tumor-specific cytotoxic T-lymphocytes (CTL,1). The generation of these CTL requires a number of essential components including the presence of tumor antigens, specialized antigen presenting cells (APC) and tumor-reactive T cells (2). This protocol focuses on the administration of recombinant human GM-CSF and IL-4 to cancer patients as a means to expand and activate in vivo antigen-presenting dendritic cells (DC).